Because I -promised to look it up, here’s a brief history of merkins from Wikipedia–
A merkin (first use, according to the OED, 1617) is a pubic wig, originally worn by prostitutes after shaving their genitalia to eliminate lice or disguise the marks of syphilis. Also many women used them so they didn’t have to hide the fact that they had shaved their genitalia. There are many different ways of wearing a merkin, although most involve placing the merkin on the vulva or the scrotum.
The term is also applied to decorative (typically sequinned) patches commonly sold in sets with nipple tassels or “pasties” and are enjoying new popularity as part of the costume of new burlesque adult entertainment.
In American cinema, merkins are currently used in films where they are worn by actors and actresses to prevent inadvertent exposure of the genitalia during nude or semi-nude scenes. If no merkin were worn, it would be necessary to restrict the shot to exclude the genital area; with the merkin in place brief flashes of the crotch can be used if necessary. The presence of the merkin protects the actor from inadvertently performing ‘full-frontal’ nudity (their contract may specifically require that nipples and genitals be covered in some way), and can help ensure that the film achieves a more “acceptable” MPAA rating.
Houghton Mifflin’s American Heritage Dictionary of the English Language, 4th edition describes the term’s etymology as stemming from an “alteration of obsolete malkin, lower-class woman, mop, from Middle English; from Malkin, diminutive of the personal name Matilda.”
It has also been suggested that, in the period when male actors played female parts, they would cover their genitals with a merkin so they could expose themselves as women in bawdy scenes.
A “short and curly history of the merkin” in The Guardian provided a partial history of the merkin. It highlighted “comedy terrorist” Aaron Barschak’s flashing of a merkin to onlookers.
The Oxford Companion to the Body dates the origin of the pubic wig back to 1450, claiming that women would shave their pubic hair and wear a merkin to combat pubic lice, and that prostitutes would wear them to cover up signs of disease. This book also mentions the tale of one man that gave a cardinal of the Catholic Church a merkin that he had acquired from a prostitute and then combed and dried. He claimed it was St. Peter’s beard.